Multiplexed charge discharge battery management system

ABSTRACT

A battery management system comprising: at least one battery comprising two or more sets of cells, each set of cells comprising one or more cells; a multiplexing switch apparatus connected to each set of cells; and at least one controller configured to use the multiplexing switch apparatus to selectively discharge the sets of cells based on at least one criterion. A battery pack comprising: at least one battery comprising two or more sets of cells, each set of cells comprising one or more cells; and an integrated switching control system comprising at least one switch connected to each set of cells, wherein the integrated switching control system is configured to control the at least one switch to discharge the sets of cells sequentially or selectively based on at least one criterion. A battery management method or a battery pack control method.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Application No. 62/712,761, filed Jul. 31, 2018, andentitled “Multiplexed Charge Discharge Battery Management System,” whichis incorporated herein by reference in its entirety for all purposes.

TECHNICAL FIELD

Charge/discharge management of electrochemical cells, and relatedsystems, are generally described.

BACKGROUND

Conventionally, batteries have failed to compete successfully withestablished power sources such as combustion engines in variousindustries, such as vehicles. One reason for this failure has been thatbattery users have been dissatisfied with the longevity and performancethat batteries have conventionally provided.

SUMMARY

Some embodiments of the invention are directed to a battery managementsystem comprising: at least one battery comprising two or more sets ofcells, each set of cells comprising one or more cells; a multiplexingswitch apparatus connected to each set of cells; and at least onecontroller configured to use the multiplexing switch apparatus toselectively discharge the sets of cells based on at least one criterion.

Some other embodiments are directed to a battery pack comprising: atleast one battery comprising two or more sets of cells, each set ofcells comprising one or more cells; and an integrated switching controlsystem comprising at least one switch connected to each set of cells,wherein the integrated switching control system is configured to controlthe at least one switch to discharge the sets of cells sequentially.

Still other embodiments are directed to a battery pack comprising: atleast one battery comprising two or more sets of cells, each set ofcells comprising one or more cells; and an integrated switching controlsystem comprising at least one switch connected to each set of cells,wherein the integrated switching control system is configured to controlthe at least one switch to selectively discharge the sets of cells basedon at least one of: a duration of a connection between a load and a setof cells currently connected to the load, a delivered discharge capacityat the connection, and a value of a function having one or moreparameters.

Further embodiments are directed to a battery management method. Themethod may comprise using a multiplexing switch apparatus, which isconnected to two or more sets of cells of at least one battery, toselectively discharge each set of cells based on at least one criterion.In some embodiments, each set of cells may comprise one or more cells.

Additional embodiments are directed to a battery pack control method.The method may comprise using an integrated switching control systemcomprising at least one switch connected to each set of cells of two ormore sets of cells of at least one battery, to control the at least oneswitch to discharge the sets of cells sequentially. In some embodiments,each set of cells may comprise one or more cells.

Some other embodiments are directed to a battery pack control methodcomprising using an integrated switching control system comprising atleast one switch connected to each set of cells of two or more sets ofcells of at least one battery, to control the at least one switch toselectively discharge the sets of cells based on at least one of: aduration of a connection between a load and a set of cells currentlyconnected to the load, a delivered discharge capacity at the connection,and a value of a function having one or more parameters, wherein eachset of cells comprises one or more cells.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIG. 1 is a block diagram illustrating a representative batterymanagement system, according to some embodiments.

FIG. 2 is a block diagram illustrating a representative battery pack,according to some embodiments.

FIG. 3A is a block diagram illustrating a representative batterymanagement system, according to some embodiments.

FIG. 3B is a block diagram illustrating a representative cell set andcorresponding components, according to some embodiments.

FIG. 3C is a cross-sectional schematic diagram illustrating theapplication of an anisotropic force to one or more electrochemicalcells, according to some embodiments.

FIG. 3D is a cross-sectional schematic diagram of electrochemical cells,according to some embodiments.

FIG. 4A is a flow chart depicting a representative process fordischarging sets of cells of a battery, according to some embodiments.

FIG. 4B is a flow chart depicting an additional representative processfor discharging sets of cells of a battery, according to someembodiments.

FIG. 5 is a flow chart depicting a representative process forcontrolling a battery pack, according to some embodiments.

FIG. 6 is a flow chart depicting an additional representative processcontrolling a battery pack, according to some embodiments.

FIG. 7A is a chart depicting an exemplary discharge profile, accordingto some embodiments.

FIG. 7B is a chart depicting an exemplary full discharge profile,according to some embodiments.

FIG. 7C is a chart depicting an exemplary battery cycle life, accordingto some embodiments.

FIG. 8 is a block diagram depicting a representative computing systemthat may be used to implement certain aspects.

DETAILED DESCRIPTION

The inventors have recognized and appreciated that conventionaltechniques for battery management have resulted in the previously poorlongevity and performance of batteries. For example, batteries havesuffered a short cycle life (e.g., a low number of complete charge anddischarge cycles before capacity falls below 80% of original capacity),particularly where charge and discharge rates are similar, or where thecharge rate is higher than the discharge rate. For example, many usersof batteries have desired batteries to have nearly identical charge anddischarge rates (e.g., 4 hours to charge and 4 hours to discharge), andbattery manufacturers have provided batteries and battery managementsystems that provide such nearly identical rates. Many users have alsodesired batteries to charge at higher rates than they discharge (e.g.,30 minutes to charge and 4 hours to discharge), such as to reduceinconvenience of waiting for charging to use the batteries.

The inventors have recognized and appreciated that the cycle life ofbatteries, and consequently the longevity and performance of batteries,may be greatly improved by employing higher ratios of discharge rate tocharge rate. Furthermore, the inventors have recognized and appreciatedthat these ratios may be employed by providing a battery managementsystem that controls the cells within the batteries to provide suchratios. For example, some embodiments are directed to a batterymanagement system that multiplexes cells such that the cells can becharged all at once or with multiple at a time and dischargedindividually or in smaller sets. This may result in actual ratios ofdischarge rate to charge rate for the cells that improve their cyclelife, while providing whatever output rates that are desired or requiredfor particular loads and applications. Furthermore, the inventors haverecognized and appreciated that discharging some but not all of thecells at once with homogeneous current distribution may also improvetheir cycle life.

For example, with a battery having 4 cells, 1 cell could be dischargedat a time at 0.5 amps for 3 hours each, and then all 4 cells could becharged at 0.5 amps for 12 hour—such a configuration would provide anactual ratio of discharge rate to charge rate of 4:1, while the ratiofrom the user's perspective would be 1:1 because the cells aredischarged individually for 3 hours each (totaling 12 hours of dischargetime). The inventors have recognized and appreciated that such a batterymanagement system may actually improve the cycle life of batteries whilestill providing users what they desire or need from the batteries. Insome embodiments, the functionality providing this duo of benefits maybe hidden from users and may be integrated into the cell blocks and/orbatteries themselves.

The inventors have recognized and appreciated that the cycle life ofbatteries may be further improved by monitoring the cycles of the cellsand various properties (such as the duration of a connection between aload and a cell or cells currently connected to the load, or a morecomplex function considering multiple parameters) and selecting whichcells to discharge when based on this monitoring, especially compared toconventional techniques, which relied on much simpler selectionprocesses like “round robin” or considering a number of prior dischargecycles.

FIG. 1 depicts a representative battery management system 100. In someembodiments, representative system 100 may include a multiplexing switchapparatus (e.g., 112), a controller (e.g., 114), one or more sensors(e.g., 116), and one or more batteries (e.g., 120, 130, 140, 150, and soon). It should be appreciated that although only a single multiplexingswitch apparatus 112, controller 114, sensor 116, and only fourbatteries 120-150 are shown in FIG. 1, any suitable number of thesecomponents may be used. Any of numerous different modes ofimplementation may be employed. Furthermore, although a label in thesingular is used herein to reference a multiplexing switch apparatus, itshould be appreciated that the components used for the multiplexing andswitching described herein may be distributed across any suitable numberof devices (e.g., switches).

According to some embodiments, the battery or batteries may include atleast one lithium-metal battery. Additionally, the battery or batteries(e.g., 120-150) may respectively include one or more cell sets (e.g.,121-124, 131-132, 141-142, 151-152, and so on), referred to also as setsof cells. In some embodiments, two or more sets of cells are included ineach battery, such as 121-122 and so on. Additionally, each set of cells(e.g., cell set 121) may include one or more cells (e.g., 121A-121C). Insome embodiments, each set of cells may have a single cell.Alternatively, each set of cells may include multiple cells and may forma cell “block,” or multiple sets of cells may together form a cellblock. Additionally, each cell (either in a battery, all the batteriesin a battery pack, or in a set of cells) or set of cells may utilize thesame electrochemistry. That is to say, in some embodiments, each cellmay make use of the same anode active material and the same cathodeactive material.

In some embodiments, a multiplexing switch apparatus (e.g., 112) mayinclude an array of switches, such as those further described inrelation to FIGS. 3A and 3B below. Additionally, the multiplexing switchapparatus may be connected to each set of cells and/or to each cellindividually. In some embodiments, the controller, such as 114, may usethe multiplexing switch apparatus to selectively discharge the cells orsets of cells based on at least one criterion.

For example, the criterion may include a sequence in which to dischargethe cells or sets of cells, such as a predefined numbering or orderassociated with the sets of cells (e.g., starting with a first set,switching through each set to the last set, and then starting over withthe first set), and/or an order based on the cell(s) or set(s) of cellswith the next highest voltage or some other measure indicating the nextstrongest. The inventors have recognized and appreciated that using asequence, especially a predefined numbering, may reduce the complexityof the operations performed by the system (e.g., a controller that isnot a microprocessor) and may be usable by a wider array of systems.

Alternatively or additionally, the criterion may be context-sensitive,such as by considering any one or more of the following: a duration of aconnection between a load and a set of cells currently connected to theload (which may be at least 0.01 seconds in some embodiments), adelivered discharge capacity at the connection, and the value of afunction having one or more parameters. In certain embodiments, thecriterion may not include a number of prior discharge cycles of the setof cells.

In some embodiments, the function may have parameters such as any one ormore of the following: a capacity accumulated over several connectionsbetween the load and the set of cells, the delivered discharge capacityat the connection, a current of the set of cells, a voltage of the setof cells and/or of at least one other set of cells, a cutoff dischargevoltage of the set of cells, a power of the set of cells, an energy ofthe set of cells, a number of charge or discharge cycles of the set ofcells, an impedance of the set of cells, a rate of voltage fading of theset of cells during the connection, a temperature of the set of cells,and a pressure of the set of cells (e.g., the pressure on the cell(s)from their physical enclosure, which may indicate cell capacity and isdiscussed further below). According to some embodiments, the delivereddischarge capacity at a single connection may be in the range from 0.01%of nominal capacity to 100% (e.g., 95%) of set nominal capacity.

In some embodiments, a sensor (e.g., 116) may measure the criterionand/or any of the parameters of the function. For example, the sensormay include a current sensor that measures the current in amperes of agiven set of cells. It should be appreciated that the criterion may beplural or singular and may relate to the currently discharging set ofcells and/or may determine the next set of cells.

In some embodiments, the controller (e.g., 114) may include one or moreprocessors, which may be of whatever complexity is suitable for theapplication. For example, evaluating the function of the criterion insome embodiments may rely on a microprocessor forming part or all of thecontroller.

In some embodiments, the controller may use the multiplexing switchapparatus to selectively discharge and charge the cells or sets of cellsat different, programmable rates. For example, the controller may usethe multiplexing switch apparatus to selectively discharge the cells orsets of cells at a first rate at least 2 times higher than a second rateof charging the sets of cells (i.e., discharging twice as fast ascharging). Alternatively or additionally, the first rate of dischargingmay be at least 4 times higher than the second rate of charging the setsof cells (i.e., discharging four times as fast as charging). Theinventors have recognized and appreciated that such ratios of dischargerate to charge rate may improve the performance and cycle life of thecells.

According to some embodiments, the controller may temporally overlap thedischarge of the sets of cells. For example, before a given cell or setof cells ceases discharging, another cell or set of cells may begindischarging. In some embodiments, the controller may continue to providepower from the sets of cells during switching between different sets.The inventors have recognized and appreciated that this temporal overlapof discharging and continuation of power may maintain the powerrequirements of the load even during transition between different cellsof sets of cells, which may further improve the cycle life of thecell(s) compared to conventional techniques. Accordingly, multiple cellsmay discharge simultaneously during such an overlap. Additionally, suchan overlap may provide smoother transition of voltage than has beenpossible with conventional techniques.

In some embodiments, the load may be at least one component of avehicle. The vehicle may be any suitable vehicle, adapted for travel onland, sea, and/or air. For example, the vehicle may be an automobile,truck, motorcycle, boat, helicopter, airplane, and/or any other suitabletype of vehicle.

Alternatively or additionally, the controller may use the multiplexingswitch apparatus (e.g., 112) to connect the sets of cells to a load in atopology employed or required by the load.

In some embodiments, the controller may use the multiplexing switchapparatus (e.g., 112) to isolate a single set of cells for dischargingwhile other sets of cells are not discharging. Alternatively oradditionally, a single cell may be isolated at a time. For example, thecontroller may use the multiplexing switch apparatus to isolate a singleset of cells or a single cell for discharging while the other cells orsets of cells are not discharging. For a given cycle, each cell may bedischarged once before any cell is discharged twice, according to someembodiments (e.g., where sequential discharging is used, but not limitedto such embodiments).

As for charging, in some embodiments the controller may use themultiplexing switch apparatus to charge the sets of cells, and/or cellswithin a set, in parallel. For example, all the cells in the cell block,battery, or batteries may be charged in parallel at a rate one-fourth ofthe rate of discharge.

FIG. 2 depicts a representative battery pack 210. In some embodiments,representative battery pack 210 may include a switching control system(e.g., 218) and one or more batteries (e.g., 120, 130, 140, 150, and soon). It should be appreciated that although only a single switchingcontrol system 218 and only four batteries 120-150 are shown in FIG. 2,any suitable number of these components may be used. Any of numerousdifferent modes of implementation may be employed. Furthermore, althougha label in the singular is used herein to reference a switching controlsystem, it should be appreciated that the components used for thecontrol and switching described herein may be distributed across anysuitable number of devices (e.g., switches, controller(s), etc.).

In some embodiments, a switching control system (e.g., 218) may includean array of switches, such as those further described in relation toFIGS. 3A and 3B below, and it may include a controller. Additionally,the switching control system may be connected to each set of cellsand/or to each cell of the batteries individually, as discussedregarding FIG. 1 above. In some embodiments, the switching controlsystem may be integrated into the battery pack. Additionally, theswitching control system may control the switch(es) (such as in a switcharray) to discharge the cells or sets of cells sequentially, such as ina predefined order associated with the cells or sets of cells.Alternatively or additionally, the switching control system may controlthe switch(es) to discharge the cells or sets of cells based on any oneor more of the following: a duration of a connection between a load anda set of cells currently connected to the load (which may be at least0.01 seconds in some embodiments), a delivered discharge capacity at theconnection, and the value of a function. In certain embodiments, thebasis for the control may not include a number of prior discharge cyclesof the set of cells.

According to some embodiments, the switching control system may performany number of other functions, such as those of the controller describedin relation to FIG. 1 above.

It should be appreciated that any of the components of representativesystem 100 or representative battery pack 210 may be implemented usingany suitable combination of hardware and/or software components. Assuch, various components may be considered a controller that may employany suitable collection of hardware and/or software components toperform the described function.

FIG. 3A depicts a representative battery management system 300. In someembodiments, representative system 300 may include any suitable numberof multi-cell blocks (e.g., 321-325), a battery cell block arrangementand balance switch configuration (e.g., 326), a battery managementmicrocontroller (e.g., 327), a battery system interface (e.g., 328),battery power terminals (e.g., 329), and a sensor (e.g., 360). Themulti-cell blocks may be connected to the battery cell block arrangementand balance switch configuration. The multi-cell blocks may also beconnected to the battery management microcontroller.

In some embodiments, the battery cell block arrangement and balanceswitch configuration may include switch multiplexing, which may connectthe cell blocks (e.g., 321-325) in the series, parallel,serial/parallel, or any other suitable topology required to meet thevoltage and current requirements of a given application or load.

According to some embodiments, the battery management microcontrollermay monitor and control the charging and discharging of the batterymanagement system to ensure the safe operation of the system and itscomponents. Additionally, the battery management microcontroller maycommunicate with a user (e.g., a consumer using the system to power aload) as well as with any suitable internal production, calibration, andtest equipment. For example, the battery management microcontroller maybe connected to the battery system interface (e.g., 328), which mayprovide the interface required for the battery managementmicrocontroller to communicate with the user as well as internalproduction, calibration, and test equipment, and any other suitableentity.

In some embodiments, the sensor may be connected to the battery cellblock arrangement and balance switch configuration, the batterymanagement microcontroller, and/or the battery power terminals, and itmay the measure attributes of the multi-cell blocks and/or any othercomponent of the system. For example, the sensor may measure attributesof the multi-cell blocks that form a criterion and/or any of theparameters of a function as described above. For example, the sensor mayinclude a current sensor that measures the current in amperes of a givenset of cells.

It should be appreciated that although battery cell block arrangementand balance switch configuration 326, battery management microcontroller327, battery system interface 328, and sensor 360 appear in singularform, and only five multi-cell blocks 321-325 are shown in FIG. 3A, anysuitable number of these components may be used and they may representmultiple components. Any of numerous different modes of implementationmay be employed. Indeed, although a label in the singular is used hereinto reference a battery cell block arrangement and balance switchconfiguration, it should be appreciated that the components used for thearrangement and balance switching described herein may be distributedacross any suitable number of devices (e.g., switches).

FIG. 3B depicts a representative cell set and corresponding components.In some embodiments, the representative cell set may include anysuitable number of cells (e.g., 321A-C) and may constitute a multi-cellblock, such as is described above. Additionally, the representative cellset may include cell multiplexing switches (e.g., 326A1), cell balanceswitches and resistors (e.g., 326A2), a cell block microcontroller(e.g., 327A), a battery management microcontroller interface (e.g.,328A), a sensor (e.g., 360A), and an input/output bus for the cell set(e.g., 321IO). In some embodiments, the cells may be connected to thecell balance switches and resistors, which may be connected to the cellmultiplexing switches.

In some embodiments, each cell (e.g., each of 321A-C) may be connectedto an array of the cell multiplexing switches, which may connect orisolate the given cell(s) from the input/output bus (e.g., 321IO), andwhich may connect or disconnect the given cell(s) to a balance resistor(e.g., one of the resistors in 326A2) that shares the balance bus withthe other cells. Additionally, in discharge mode one cell (e.g., 321A)may be connected to the input/output bus and disconnected from thebalance resistor. The remaining cells (e.g., 321B-C) may be disconnectedfrom the input/output bus and connected to the corresponding balanceresistor(s). Additionally, in charge mode for some embodiments, allcells (e.g., 321A-C) may be connected to the input/output bus anddisconnected from the balance resistors 326A2.

According to some embodiments, the cell block microcontroller (e.g.,327A) may generate switching waveforms to ensure that overlap anddeadband requirements for the switching is appropriate for theapplication or load. Additionally, the cell block microcontroller maydetermine the state required by the application or load by monitoringthe cell block's voltage and current, as well as by receivingcommunication from a battery management microcontroller (e.g., 327 inFIG. 3A), to which the cell block microcontroller may be connected viathe battery management microcontroller interface.

FIG. 3C is an exemplary cross-sectional schematic illustration of anelectrochemical system in which an anisotropic force is applied to anelectrochemical cell (e.g., 321A), according to one set of embodiments.The term “electrochemical cell” is used herein to generally refer to ananode, a cathode, and an electrolyte configured to participate in anelectrochemical reaction to produce power. An electrochemical cell canbe rechargeable or non-rechargeable.

In FIG. 3C, the system may include electrochemical cell 321A and, insome embodiments, a pressure distributor 334 containing a fluidassociated with electrochemical cell 321A. Pressure distributor 334 canbe configured such that an anisotropic force is applied to a componentof electrochemical cell 321A through pressure distributor 334. Forexample, in the set of embodiments illustrated in FIG. 3C, pressuretransmitter 336 can be configured to apply an anisotropic force topressure distributor 334, which in turn causes an anisotropic force tobe applied to at least one component (e.g., an electrode) ofelectrochemical cell 321A. The system can also include a substrate 332on which the electrochemical cell is positioned. Substrate 332 cancomprise, for example, a tabletop, a surface of a container in whichelectrochemical cell 321A is housed, or any other suitable surface.

Pressure distributor 334 can be associated with electrochemical cell321A in a variety of suitable configurations to produce the inventivesystems and methods described herein. As used herein, a pressuredistributor is associated with an electrochemical cell when at least aportion of a force that is applied to and/or through the pressuredistributor can be transmitted to a component of the electrochemicalcell. For example, in certain embodiments, a pressure distributor isassociated with an electrochemical cell when the pressure distributor isin direct contact with the electrochemical cell or a component thereof.Generally, a first article and a second article are in direct contactwhen the first article and the second article are directly touching. Forexample, in FIG. 3C, pressure distributor 334 and the electrochemicalcell 321A are in direct contact.

In certain embodiments, a pressure distributor is associated with theelectrochemical cell when the pressure distributor is in indirectcontact with at least one component of the electrochemical cell.Generally, a first article and a second article are in indirect contactwhen a pathway can be traced between the first article and the secondarticle that intersects only solid and/or liquid components. Such apathway can be in the form of a substantially straight line, in certainembodiments. A pressure distributor can be in indirect contact with anelectrochemical cell, in certain embodiments, when one or more solidand/or liquid materials are positioned between them, but a force canstill be transmitted to the electrochemical cell through the pressuredistributor.

In certain embodiments, a pressure distributor is associated with anelectrochemical cell when it is located within the boundaries of acontainer at least partially (e.g., completely) enclosing the componentsof the electrochemical cell. For example, in certain embodiments,pressure distributor 334 could be positioned between an electrode and acontainer at least partially enclosing the electrochemical cell. Incertain embodiments, pressure distributor 334 could be positionedbetween a current collector and a container at least partially enclosingthe electrochemical cell. In some embodiments, pressure distributor 334can be used as a current collector, for example, positioned next to anelectrode of the electrochemical cell and within a container at leastpartially containing the electrodes and electrolyte of the electriccell. This could be achieved, for example, by fabricating pressuredistributor 334 from a material (e.g., a metal such as a metal foil, aconductive polymer, and the like) that is sufficiently electricallyconductive to transport electrons to and/or from an electrode of theelectrochemical cell.

In some embodiments, a pressure distributor is associated with anelectrochemical cell when it is located outside the boundaries of acontainer at least partially (e.g., completely) enclosing the componentsof the electrochemical cell. For example, in certain embodiments,pressure distributor 334 could be positioned in direct or indirectcontact with an exterior surface of a container at least partiallyenclosing the electrodes and electrolyte of an electrochemical cell.

In certain embodiments, the pressure distributor can be located arelatively short distance from at least one electrode of anelectrochemical cell. For example, in certain embodiments, the shortestdistance between the pressure distributor and an electrode of theelectrochemical cell is less than about 10 times, less than about 5times, less than about 2 times, less than about 1 time, less than about0.5 times, or less than about 0.25 times the maximum cross-sectionaldimension of that electrode.

In some embodiments, a pressure distributor can be associated with aparticular electrode (e.g., an anode) of an electrochemical cell. Forexample, a pressure distributor can be in direct or indirect contactwith an electrode (e.g., an anode such as an anode comprising lithium)of an electrochemical cell. In certain embodiments, the pressuredistributor can be positioned outside a container at least partiallycontaining the electrode but still associated with the electrode, forexample, when only liquid and/or solid components separate the electrodefrom the pressure distributor. For example, in certain embodiments inwhich the pressure distributor is positioned in direct or indirectcontact with a container at least partially enclosing the electrode anda liquid electrolyte, the pressure distributor would be associated withthe electrode.

In certain embodiments, a force can be applied to electrochemical cell321A or a component of electrochemical cell 321A (e.g., an electrode ofthe electrochemical cell) through pressure distributor 334. As usedherein, a force is applied to a first component (e.g., anelectrochemical cell) through a second component (e.g., a pressuredistributor) when the second component at least partially transmits aforce from the source of the force to the first component.

A force can be applied to an electrochemical cell or a component thereofthrough a pressure distributor in a variety of ways. In certainembodiments, applying a force to a pressure distributor comprisesapplying a force to an external surface of the pressure distributor.This can be achieved, for example, via pressure transmitter 336. Forexample, in FIG. 3C, pressure transmitter 336 can be positioned to applyan anisotropic force to electrochemical cell 321A through pressuredistributor 334 by applying a force to surface 340 of pressuredistributor 334. As used herein, a first component is positioned toapply an anisotropic force to a second component when the first andsecond components are positioned such that at least a portion of a forcethat is applied to and/or through the first component can be transmittedto the second component. In certain embodiments, pressure transmitterand the pressure distributor are in direct contact. In some embodiments,one or more materials (e.g., one or more solid and/or liquid materials)are positioned between the pressure transmitter and the pressuredistributor, but a force can still be applied to the pressuredistributor by the pressure transmitter. In certain embodiments, thepressure transmitter and the pressure distributor can be in indirectcontact such that a continuous pathway can be traced through solidand/or liquid materials from the pressure distributor to theelectrochemical cell. Such a pathway can be substantially (e.g.,completely) straight, in certain embodiments.

In the set of embodiments illustrated in FIG. 3C, pressure transmitter336 and electrochemical cell 321A are positioned on opposite sides ofpressure distributor 334. Accordingly, when an anisotropic force (e.g.,an anisotropic force in the direction of arrow 150) is applied to and/orby pressure transmitter 336 to surface 340, the force can be transmittedthrough pressure distributor 334 onto surface 342 of electrochemicalcell 321A, and to the components of electrochemical cell 321A.

In some embodiments, applying a force to a pressure distributorcomprises applying a force to an internal surface of the pressuredistributor. For example, in certain embodiments, a force can be appliedthrough the pressure distributor to the electrochemical cell bymaintaining and/or increasing the pressure of the fluid within thepressure distributor. In the set of embodiments illustrated in FIG. 3C,a force can be applied through pressure distributor 334 toelectrochemical cell 321A by transporting additional fluid through aninlet (not shown) of pressure distributor 334 (e.g., by inflatingpressure distributor 334). In some such embodiments, when the pressurewithin a pressure distributor is maintained and/or increased, themovement of pressure transmitter can be restricted such that a force isproduced on an external surface of the electrochemical cell and/or on acomponent of the electrochemical cell (e.g., an active surface of anelectrode within the electrochemical cell). For example, in FIG. 3C, asadditional fluid is added to pressure distributor 334, pressuretransmitter 336 can be configured to restrict the movement of theboundaries of pressure distributor 334 such that a force is applied tosurface 342 of electrochemical cell 321A.

In certain embodiments, fluid can be added to pressure distributor 334before it is positioned between electrochemical cell 321A and pressuretransmitter 336. After the fluid has been added, pressure distributor334 can be compressed and positioned between electrochemical cell 321Aand pressure transmitter 336, after which, the compression of the fluidwithin pressure distributor 334 can produce a force that is applied tosurface 342 of electrochemical cell 321A (and, accordingly, to a surfaceof one or more components of the electrochemical cell, such as an activesurface of an electrode). One of ordinary skill in the art, given thepresent disclosure, would be capable of designing additional systems andmethods by which a force can be applied to an electrochemical cellthrough a pressure distributor.

The fluid within pressure distributor 334 can allow the pressure that istransmitted through pressure distributor 334 to be applied relativelyevenly across the surface 342 of electrochemical cell 321A (and,accordingly, relatively evenly across a surface of one or morecomponents of the electrochemical cell, such as an active surface of anelectrode). Not wishing to be bound by any particular theory, it isbelieved that a presence of a fluid within pressure distributor 334reduces and/or eliminates points of relatively high pressure on surface342 as fluid within relatively high pressure regions is transported toregions of relatively low pressure.

In some embodiments, the degree to which the pressure distributor evenlydistributes the force applied to electrochemical cell can be enhanced ifthe external surface of the pressure transmitter is appropriatelyaligned with an external surface of the electrochemical cell or acontainer thereof. For example, in the set of embodiments illustrated inFIG. 3C, external surface 340 of pressure transmitter 336 faces externalsurface 342 of electrochemical cell 321A. In certain embodiments, theexternal surface of the pressure transmitter is substantially parallelto the external surface of the electrochemical cell to which a force isapplied. For example, in the set of embodiments illustrated in FIG. 3C,external surface 340 of pressure transmitter 336 is substantiallyparallel to external surface 342 of electrochemical cell 321A. As usedherein, two surfaces are substantially parallel to each other when thetwo surfaces form angles of no greater than about 10 degrees. In certainembodiments, two substantially parallel surfaces form angles of nogreater than about 5 degrees, no greater than about 3 degrees, nogreater than about 1 degree, or no greater than about 0.1 degree.

The pressure distributor can have a variety of suitable forms. Incertain embodiments, the pressure distributor can comprise a bag orother suitable container in which a fluid is contained. In someembodiments, the pressure distributor can comprise a bellows that isconfigured to deform along the direction in which the force is appliedto the pressure distributor.

The pressure distributor container can be made of a variety ofmaterials. In certain embodiments, the pressure distributor containercan comprise a flexible material. For example, in certain embodiments,the pressure distributor container can comprise a polymer such aspolyethylene (e.g., linear low density and/or ultra-low densitypolyethylene), polypropylene, polyvinylchloride, polyvinyldichloride,polyvinylidene chloride, ethylene vinyl acetate, polycarbonate,polymethacrylate, polyvinyl alcohol, nylon, silicone rubber (e.g.,polydimethylsiloxane), and/or other natural or synthetic rubbers orplastics. In certain embodiments (e.g., in embodiments in which a gas isused as the fluid within the pressure distributor), the pressuredistributor container can include a metal layer (e.g., an aluminum metallayer), which can enhance the degree to which fluid (e.g., a gas) isretained within the pressure distributor. The use of flexible materialscan be advantageous, in certain embodiments, as they may allow forredistribution of the contents of the pressure distributor relativelyeasily, enhancing the degree to which the force is uniformly applied.

In some embodiments, the pressure distributor can comprise an elasticmaterial. In certain embodiments, the elasticity of the material fromwhich the pressure distributor is fabricated can be selected such thatthe pressure distributor transmits a desirable amount of a force appliedto the pressure distributor to an adjacent component. To illustrate, incertain cases, if the pressure distributor is made of a very flexiblematerial, a relatively high percentage of the force applied to thepressure distributor might be used to elastically deform the pressuredistributor material, rather than being transmitted to an adjacentelectrochemical cell. In certain embodiments, the pressure distributorcan be formed of a material having a Young's modulus of less than about1 GPa. One of ordinary skill in the art would be capable of measuringthe Young's modulus of a given material by performing, for example, atensile test (also sometimes referred to a tension test). Exemplaryelastic polymers (i.e., elastomers) that could be used include thegeneral classes of silicone polymers, epoxy polymers, and acrylatepolymers.

In certain embodiments, the pressure distributor comprises an enclosedcontainer containing a fluid. The pressure distributor can comprise anopen container containing a fluid, in certain embodiments. For example,in some embodiments, the pressure distributor comprises a containerfluidically connected to a device constructed and arranged to transportthe fluid through the pressure distributor, as described in more detailbelow.

A variety of fluids can be used in association with the pressuredistributor. As used herein, a “fluid” generally refers to a substancethat tends to flow and to conform to the outline of its container.Examples of fluids include liquids, gases, gels, viscoelastic fluids,solutions, suspensions, fluidized particulates, and the like. Typically,fluids are materials that are unable to withstand a static shear stress,and when a shear stress is applied, the fluid experiences a continuingand permanent distortion. The fluid may have any suitable viscosity thatpermits flow and redistribution of an applied force.

In certain embodiments, the fluid within the pressure distributorcomprises a gas (e.g., air, nitrogen, a noble gas (e.g., helium, neon,argon, krypton, xenon), a gas refrigerant, or mixtures of these). Incertain embodiments, the gas within the pressure distributor cancomprise a relatively high molecular weight (e.g., at least about 100g/mol), which can limit the degree to which gas permeates through thewalls of the pressure distributor. In some embodiments, the fluid withinthe pressure distributor comprises a liquid including, but not limitedto, water, an electrolyte (e.g., a liquid electrolyte similar oridentical to that used in the electrochemical cell), greases (e.g.,petroleum jelly, Teflon grease, silicone grease), oils (e.g., mineraloil), and the like. In certain embodiments, the fluid within thepressure distributor comprises a gel. Suitable gels for use within thepressure distributor include, but are not limited to, hydrogels (e.g.,silicone gel), organogels, or xerogels. In certain embodiments, thefluid comprises a fluidized bed of solid particles (e.g., sand, powders,and the like). Fluidization can be achieved, for example, by passing agas and/or a liquid through the particles and/or by vibrating asubstrate on which the particles are positioned such that the particlesmove relative to each other.

The fluid used in association with the pressure distributor can have anysuitable viscosity. In certain embodiments, a Newtonian fluid can beused within the pressure distributor, although the invention is not solimited, and non-Newtonian fluids (e.g., a shear thinning fluid, a shearthickening fluid, etc.) can also be used. In certain embodiments, thepressure distributor can contain a Newtonian fluid with a steady-stateshear viscosity of less than about 1×10⁷ centipoise (cP), less thanabout 1×10⁶ cP, less than about 1×10⁵ cP less than about 1000 cP, lessthan about 100 cP, less than about 10 cP, or less than about 1 cP (and,in some embodiments, greater than about 0.001 cP, greater than about0.01 cP, or greater than about 0.1 cP) at room temperature.

In certain embodiments, the fluid within the pressure distributor can beselected such that it is suitable for being transported into and/or outof the pressure distributor. For example, in certain embodiments, fluidmay be transported into the pressure distributor to apply an anisotropicforce to the electrochemical cell (e.g., by compressing the fluid withinthe pressure distributor when it is positioned between theelectrochemical cell and the pressure transmitter). As another example,a fluid may be transported into and/or out of a pressure distributor totransfer heat to and/or away from a component of the system.

Pressure transmitter 336 can also adopt a variety of configurations. Incertain embodiments, pressure transmitter 336 is moveable relative toelectrochemical cell 321A. In some such embodiments, a force can beapplied to electrochemical cell 321A through pressure distributor 334 bymoving pressure transmitter 336 closer to electrochemical cell 321Aand/or maintaining the separation between electrochemical cell 321A andpressure transmitter 336. As one particular example, in some embodimentsthe pressure transmitter 336 includes a compression spring, a firstapplicator structure, and a second applicator structure. Firstapplicator structure can correspond to, for example, a flat plate ofrigid material, or any other suitable structure. Second applicatorstructure can correspond to, for example, a second plate of rigidmaterial, a portion of a wall of a container in which theelectrochemical cell is housed, or any other suitable structure. In someembodiments, a force can be applied to surface 342 of electrochemicalcell 321A when a compression spring is compressed between applicatorstructure and applicator structure. In certain embodiments, Bellevillewashers, machine screws, pneumatic devices, weights, air cylinders,and/or hydraulic cylinders could be used in place of, or in addition to,the compression spring. In some embodiments, a force can be applied toan electrochemical cell using a constricting element (e.g., an elasticband, a turnbuckle band, etc.) arranged around one or more externalsurfaces of the electrochemical cell. A variety of suitable methods forapplying a force to an electrochemical cell are described, for example,in U.S. Patent Publication No. 2010/0035128 to Scordilis-Kelley et al.filed on Aug. 4, 2009, entitled “Application of Force in ElectrochemicalCells,” which is incorporated herein by reference in its entirety forall purposes.

In certain embodiments, pressure transmitter 336 is not substantiallymoveable relative to electrochemical cell 321A, and a force can beapplied to the electrochemical cell, for example, by pressurizing thepressure distributor 334. In some such embodiments, pressurizing thepressure distributor can result in the application of a force to theelectrochemical cell because the substantially immovable pressuretransmitter 336 restricts the movement of one or more of the boundariesof pressure distributor 334, thereby applying an anisotropic force toelectrochemical cell 321A.

In certain embodiments, pressure transmitter comprises all or part of asubstantially rigid structure (e.g., a package enclosing anelectrochemical cell), and the movement of the pressure transmitter canbe restricted by the degree to which the substantially rigid structureis inflexible. In certain embodiments, the pressure transmitter cancomprise a structure that is integrated with at least a portion of theother components of the system, which can restrict its movement. Forexample, in certain embodiments, the pressure transmitter can compriseat least a portion of one or more walls of a package within whichelectrochemical cell 321A and pressure distributor 334 are positioned.As one particular example, pressure transmitter 336 might form a firstwall of a package containing electrochemical cell 321A while substrate332 forms a second wall (e.g., opposite to the first wall) of thepackage. In certain embodiments, the movement of pressure transmitter336 can be restricted by applying a force within and/or on the pressuretransmitter such that its movement is restricted. In any of these cases,a force can be applied to the electrochemical cell, in certainembodiments, by adding fluid to and/or maintaining the amount of fluidwithin pressure distributor 334.

FIG. 3C illustrates a set of embodiments in which a single pressuretransmitter and a single pressure distributor are used to apply a forceto an electrochemical cell. In certain embodiments, however, more thanone pressure distributor and/or more than one pressure transmitter canbe employed. For example, in some embodiments, the system includes asecond pressure distributor positioned under electrochemical cell 321Aand a second pressure transmitter positioned under the second pressuredistributor. In certain embodiments, a substantially evenly distributedforce can be applied to an external surface of electrochemical cell 321Athrough the second pressure distributor, for example, by applying aforce to and/or through the second pressure transmitter and onto asurface of the second pressure distributor.

In some embodiments, fluid can be transported into and/or out of thepressure distributor to transport heat to and/or away fromelectrochemical cell 321A. For example, pressure distributor 334 mayinclude an inlet and an outlet configured to transport a fluid throughpressure distributor 334. As fluid is transported through pressuredistributor 334, it can absorb heat from electrochemical cell 321A andtransport it away from the system via the outlet. Any suitable devicecan be used to transport the fluid through the pressure distributor suchas, for example, a pump, a vacuum, or any other suitable device.

In certain embodiments, the fluid used in association with the pressuredistributor can be selected such that it cools or heats the system to adesired degree. For example, in certain embodiments, the fluid withinthe pressure distributor can comprise a coolant such as water, ethyleneglycol, diethylene glycol, propylene glycol, polyalkylene glycols(PAGs), oils (e.g., mineral oils, castor oil, silicone oils,fluorocarbon oils, and/or refrigerants (e.g., freons,chlorofluorocarbons, perfluorocarbons, and the like).

The embodiments described herein can be used with a variety ofelectrochemical cells. While primary (disposable) electrochemical cellsand secondary (rechargeable) electrochemical cells can be used inassociation with the embodiments described herein, some embodimentsadvantageously make use of secondary electrochemical cells, for example,due to the benefits provided by uniform force application during the(re)charging process. In certain embodiments, the electrochemical cellcomprises a lithium-based electrochemical cell such as a lithium-sulfurelectrochemical cell (and assemblies of multiple cells, such asbatteries thereof).

Although the present invention can find use in a wide variety ofelectrochemical devices, an example of one such device is provided inFIG. 3D for illustrative purposes only. In FIG. 3D, a general embodimentof electrochemical cell 321A includes cathode 310, anode 312, andelectrolyte 314 in electrochemical communication with the cathode andthe anode.

In some cases, electrochemical cell 321A may optionally be at leastpartially contained by containment structure 316. Containment structure316 may comprise a variety of shapes including, but not limited to,cylinders, prisms (e.g., triangular prisms, rectangular prisms, etc.),cubes, or any other shape. In certain embodiments, a pressuredistributor can be associated with electrochemical cell 321A bypositioning the pressure distributor outside containment structure 316,in either direct or indirect contact with surface 318A and/or surface318B. When positioned in this way, the pressure distributor can beconfigured to apply a force, directly or indirectly, to surfaces 318Aand/or 318B of containment structure 316, as described above. In certainembodiments, a pressure distributor can be positioned between cathode310 and containment structure 316, or between anode 312 and containmentstructure 316. In some such embodiments, containment structure can actas a pressure transmitter and/or a separate pressure transmitter can beconfigured to apply a force to the pressure distributor via thecontainment structure.

A typical electrochemical cell system also would include, of course,current collectors, external circuitry, and the like. Those of ordinaryskill in the art are well aware of the many arrangements that can beutilized with the general schematic arrangement as shown in the figuresand described herein.

The components of electrochemical cell 321A may be assembled, in somecases, such that the electrolyte is located between the cathode and theanode in a planar configuration. For example, in the embodimentsillustrated in FIG. 3D, cathode 310 of electrochemical cell 321A issubstantially planar. A substantially planar cathode can be formed, forexample, by coating a cathode slurry on a planar substrate, such as ametal foil or other suitable substrate, which may be included in theassembly of electrochemical cell 321A (although not illustrated in FIG.3D) or removed from cathode 310 prior to assembly of the electrochemicalcell. In addition, in FIG. 3D, anode 312 is illustrated as beingsubstantially planar. A substantially planar anode can be formed, forexample, by forming a sheet of metallic lithium, by forming an anodeslurry on a planar substrate, or by any other suitable method.Electrolyte 314 is also illustrated as being substantially planar inFIG. 3D.

In certain embodiments, electrochemical cell 321A can comprise anelectrode that comprises a metal such as an elemental metal and/or ametal alloy. As one particular example, in certain embodiments,electrochemical cell 321A can comprise an anode comprising elementallithium (e.g., elemental lithium metal and/or a lithium alloy). Incertain embodiments, the anisotropic force applied to theelectrochemical cell is sufficiently large such that the application ofthe force affects the surface morphology of the metal within anelectrode of the electrochemical cell, as described in more detailbelow.

While FIG. 3D illustrates an electrochemical cell arranged in a planarconfiguration, it is to be understood that any electrochemical cellarrangement can be constructed, employing the principles of the presentinvention, in any configuration. In addition to the shape illustrated inFIG. 3D, the electrochemical cells described herein may be of any othershape including, but not limited to, cylinders, a folded multi-layerstructure, prisms (e.g., triangular prisms, rectangular prisms, etc.),“Swiss-rolls,” non-planar multi-layered structures, etc. Additionalconfigurations are described in U.S. patent application Ser. No.11/400,025, filed Apr. 6, 2006, entitled, “Electrode Protection in bothAqueous and Non-Aqueous Electrochemical Cells, including RechargeableLithium Batteries,” to Affinito et al., which is incorporated herein byreference in its entirety.

In some embodiments, the cathode and/or the anode comprise at least oneactive surface. As used herein, the term “active surface” is used todescribe a surface of an electrode that is in physical contact with theelectrolyte and at which electrochemical reactions may take place. Forexample, in the set of embodiments illustrated in FIG. 3D, cathode 310includes cathode active surface 320 and anode 312 includes anode activesurface 322.

In certain embodiments, the anisotropic force applied to a pressuretransmitter 336 and/or through pressure distributor 334 (and eventuallyin some cases to surface 342 of electrochemical cell 321A) comprises acomponent normal to the active surface of an electrode (e.g., an anodesuch as an anode containing lithium metal) within the electrochemicalcell. Accordingly, applying an anisotropic force through pressuredistributor 334 to the electrochemical cell can result in an anisotropicforce being applied to an active surface of an electrode (e.g., ananode) within the electrochemical cell. In the case of a planarelectrode surface, the applied force may comprise an anisotropic forcewith a component normal to the electrode active surface at the point atwhich the force is applied. For example, referring to the set ofembodiments illustrated in FIG. 3C and FIG. 3D, an anisotropic force inthe direction of arrow 370 may be applied to electrochemical cell 321Athrough pressure distributor 334. An anisotropic force applied in thedirection of arrow 370 would include a component 372 that is normal toanode active surface 322 and normal to cathode active surface 320. Inaddition, an anisotropic force applied in the direction of arrow 370would include a component 374 that is not normal (and is in factparallel) to anode active surface 322 and cathode active surface 320.

In the case of a curved surface (e.g., a concave surface or a convexsurface), the force applied to the electrochemical cell may comprise ananisotropic force with a component normal to a plane that is tangent tothe curved surface at the point at which the force is applied.

In one set of embodiments, systems and methods of the invention areconfigured such that, during at least one period of time during chargeand/or discharge of the cell, an anisotropic force with a componentnormal to the active surface of an electrode (e.g., the anode) isapplied to the electrochemical cell. In some embodiments, the force maybe applied continuously, over one period of time, or over multipleperiods of time that may vary in duration and/or frequency.

The magnitude of the applied force is, in some embodiments, large enoughto enhance the performance of the electrochemical cell. In certainembodiments, an electrode active surface (e.g., an anode active surface)and the anisotropic force may be together selected such that theanisotropic force affects surface morphology of the electrode activesurface to inhibit an increase in electrode active surface area throughcharge and discharge and wherein, in the absence of the anisotropicforce but under otherwise essentially identical conditions, theelectrode active surface area is increased to a greater extent throughcharge and discharge cycles. “Essentially identical conditions,” in thiscontext, means conditions that are similar or identical other than theapplication and/or magnitude of the force. For example, otherwiseidentical conditions may mean a cell that is identical, but where it isnot constructed (e.g., by brackets or other connections) to apply theanisotropic force on the subject electrochemical cell.

The electrode active surface and anisotropic force can be selectedtogether, to achieve results described herein, easily by those ofordinary skill in the art. For example, where the electrode activesurface is relatively soft, the component of the force normal to theelectrode active surface may be selected to be lower. Where theelectrode active surface is harder, the component of the force normal tothe electrode active surface may be greater. Those of ordinary skill inthe art, given the present disclosure, can easily select anodematerials, alloys, mixtures, etc. with known or predictable properties,or readily test the hardness or softness of such surfaces, and readilyselect cell construction techniques and arrangements to provideappropriate forces to achieve what is described herein. Simple testingcan be done, for example by arranging a series of active materials, eachwith a series of forces applied normal (or with a component normal) tothe active surface, to determine the morphological effect of the forceon the surface without cell cycling (for prediction of the selectedcombination during cell cycling) or with cell cycling with observationof a result relevant to the selection.

As noted above, in some embodiments, an anisotropic force with acomponent normal to an electrode active surface (e.g., of the anode) isapplied, during at least one period of time during charge and/ordischarge of the cell, to an extent effective to inhibit an increase insurface area of the electrode active surface relative to an increase insurface area absent the anisotropic force. The component of theanisotropic force normal to the electrode active surface may, forexample, define a pressure of at least about 20, at least about 25, atleast about 35, at least about 40, at least about 50, at least about 75,at least about 90, at least about 100, at least about 125, at leastabout 150, at least about 200, at least about 300, at least about 400,or at least about 500 Newtons per square centimeter. In certainembodiments, the component of the anisotropic force normal to the anodeactive surface may, for example, define a pressure of less than about500, less than about 400, less than about 300, less than about 200, lessthan about 190, less than about 175, less than about 150, less thanabout 125, less than about 115, or less than about 110 Newtons persquare centimeter. While forces and pressures are generally describedherein in units of Newtons and Newtons per unit area, respectively,forces and pressures can also be expressed in units of kilograms-forceand kilograms-force per unit area, respectively. One of ordinary skillin the art will be familiar with kilogram-force-based units, and willunderstand that 1 kilogram-force is equivalent to about 9.8 Newtons.

In certain embodiments, the component of the anisotropic force normal tothe active surface of an electrode within the electrochemical celldefines a pressure that is at least about 50%, at least about 75%, atleast about 100%, at least about 120% of the yield stress of thatelectrode (e.g., during charge and/or discharge of the electrochemicalcell). In certain embodiments, the component of the anisotropic forcenormal to the active surface of an electrode within the electrochemicalcell defines a pressure that is less than about 250% or less than about200% of the yield stress of that electrode (e.g., during charge and/ordischarge of the electrochemical cell). For example, in someembodiments, the electrochemical cell can comprise an anode (e.g., ananode comprising lithium metal and/or a lithium alloy), and thecomponent of an applied anisotropic force that is normal to the anodeactive surface can define a pressure that is at least about 50%, atleast about 75%, at least about 100%, or at least about 120% of theyield stress of the anode (and/or less than about 250% or less thanabout 200% of the yield stress of the anode). In some embodiments, theelectrochemical cell can comprise a cathode, and the component of theanisotropic force normal to the cathode active surface can define apressure that is at least about 50%, at least about 75%, at least about100%, or at least about 120% of the yield stress of the cathode (and/orless than about 250% or less than about 200% of the yield stress of thecathode).

In some cases, the anisotropic force can define a pressure that isrelatively uniform across one or more external surfaces of theelectrochemical cell and/or across one or more active surfaces ofelectrode(s) within the electrochemical cell. In some embodiments, atleast about 50%, at least about 75%, at least about 85%, at least about90%, at least about 95%, or at least about 98% of the area of one ormore external surfaces of an electrochemical cell and/or of the area ofone or more active surfaces of an electrode (e.g., anode) defines auniform area that includes a substantially uniform distribution ofpressure defined by an anisotropic force. In this context, a “surface ofan electrochemical cell” and a “surface of an electrode” refer to thegeometric surfaces of the electrochemical cell and the electrode, whichwill be understood by those of ordinary skill in the art to refer to thesurfaces defining the outer boundaries of the electrochemical cell andelectrode, for example, the area that may be measured by a macroscopicmeasuring tool (e.g., a ruler) and does not include the internal surfacearea (e.g., area within pores of a porous material such as a foam, orsurface area of those fibers of a mesh that are contained within themesh and do not define the outer boundary, etc.).

In some embodiments, a pressure is substantially uniformly distributedacross a surface when any continuous area that covers about 10%, about5%, about 2%, or about 1% of the uniform area (described in thepreceding paragraph) includes an average pressure that varies by lessthan about 25%, less than about 10%, less than about 5%, less than about2%, or less than about 1% relative to the average pressure across theentirety of the uniform area.

Stated another way, in some embodiments, at least about 50% (or at leastabout 75%, at least about 85%, at least about 90%, at least about 95%,or at least about 98%) of the area of a surface of the electrochemicalcell and/or of the active area of an electrode defines a first,continuous area of essentially uniform applied pressure, the first areahaving a first average applied pressure. In some cases, any continuousarea that covers about 10% (or about 5%, about 2%, or about 1%) of thefirst, continuous area of the surface of the electrochemical cell and/orof the electrode includes a second average applied pressure that variesby less than about 25% (or less than about 10%, less than about 5%, lessthan about 2%, or less than about 1%) relative to the first averageapplied pressure across the first, continuous area.

One of ordinary skill in the art would be capable of determining anaverage applied pressure within a portion of a surface, for example, bydetermining the force level applied at a representative number of pointswithin the surface portion, integrating a 3-dimensional plot of theapplied pressure as a function of position on the surface portion, anddividing the integral by the surface area of the surface portion. One ofordinary skill in the art would be capable of producing a plot of theapplied pressure across a surface portion by, for example, using aTekscan I-Scan system for measuring the pressure field.

The anodes of the electrochemical cells described herein may comprise avariety of anode active materials. As used herein, the term “anodeactive material” refers to any electrochemically active speciesassociated with the anode. For example, the anode may comprise alithium-containing material, wherein lithium is the anode activematerial. Suitable electroactive materials for use as anode activematerials in the anode of the electrochemical cells described hereininclude, but are not limited to, lithium metal such as lithium foil andlithium deposited onto a conductive substrate, and lithium alloys (e.g.,lithium-aluminum alloys and lithium-tin alloys). Methods for depositinga negative electrode material (e.g., an alkali metal anode such aslithium) onto a substrate may include methods such as thermalevaporation, sputtering, jet vapor deposition, and laser ablation.Alternatively, where the anode comprises a lithium foil, or a lithiumfoil and a substrate, these can be laminated together by a laminationprocess as known in the art to form an anode.

In one embodiment, an electroactive lithium-containing material of ananode active layer comprises greater than 50% by weight of lithium. Inanother embodiment, the electroactive lithium-containing material of ananode active layer comprises greater than 75% by weight of lithium. Inyet another embodiment, the electroactive lithium-containing material ofan anode active layer comprises greater than 90% by weight of lithium.Additional materials and arrangements suitable for use in the anode aredescribed, for example, in U.S. Patent Publication No. 2010/0035128 toScordilis-Kelley et al. filed on Aug. 4, 2009, entitled “Application ofForce in Electrochemical Cells,” which is incorporated herein byreference in its entirety for all purposes.

The cathodes in the electrochemical cells described herein may comprisea variety of cathode active materials. As used herein, the term “cathodeactive material” refers to any electrochemically active speciesassociated with the cathode. Suitable electroactive materials for use ascathode active materials in the cathode of the electrochemical cells ofthe invention include, but are not limited to, one or more metal oxides,one or more intercalation materials, electroactive transition metalchalcogenides, electroactive conductive polymers, sulfur, carbon and/orcombinations thereof.

In some embodiments, the cathode active material comprises one or moremetal oxides. In some embodiments, an intercalation cathode (e.g., alithium-intercalation cathode) may be used. Non-limiting examples ofsuitable materials that may intercalate ions of an electroactivematerial (e.g., alkaline metal ions) include metal oxides, titaniumsulfide, and iron sulfide. In some embodiments, the cathode is anintercalation cathode comprising a lithium transition metal oxide or alithium transition metal phosphate. Additional examples includeLi_(x)CoO₂ (e.g., Li_(1.1)CoO₂), Li_(x)NiO₂, Li_(x)MnO₂, Li_(x)Mn₂O₄(e.g., Li_(1.05)Mn₂O₄), Li_(x)CoPO₄, Li_(x)MnPO₄, LiCo_(x)Ni_((1-x))O₂,and LiCo_(x)Ni_(y)Mn_((1-x-y))O₂ (e.g., LiNi_(1/3)Mn_(1/3)Co_(1/3)O₂,LiNi_(3/5)Mn_(1/5)Co_(1/5)O₂, LiNi_(4/5)Mn_(1/10)Co_(1/10)O₂,LiNi_(1/2)Mn_(3/10)Co_(1/5)O₂). X may be greater than or equal to 0 andless than or equal to 2. X is typically greater than or equal to 1 andless than or equal to 2 when the electrochemical cell is fullydischarged, and less than 1 when the electrochemical cell is fullycharged. In some embodiments, a fully charged electrochemical cell mayhave a value of x that is greater than or equal to 1 and less than orequal to 1.05, greater than or equal to 1 and less than or equal to 1.1,or greater than or equal to 1 and less than or equal to 1.2. Furtherexamples include Li_(x)NiPO₄, where (0<x≤1), LiMn_(x)Ni_(y)O₄ where(x+y=2) (e.g., LiMn_(1.5)Ni_(0.5)O₄), LiNi_(x)Co_(y)Al_(z)O₂ where(x+y+z=1), LiFePO₄, and combinations thereof. In some embodiments, theelectroactive material within the cathode comprises lithium transitionmetal phosphates (e.g., LiFePO₄), which can, in certain embodiments, besubstituted with borates and/or silicates.

As noted above, in some embodiments, the cathode active materialcomprises one or more chalcogenides. As used herein, the term“chalcogenides” pertains to compounds that contain one or more of theelements of oxygen, sulfur, and selenium. Examples of suitabletransition metal chalcogenides include, but are not limited to, theelectroactive oxides, sulfides, and selenides of transition metalsselected from the group consisting of Mn, V, Cr, Ti, Fe, Co, Ni, Cu, Y,Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, and Ir. In oneembodiment, the transition metal chalcogenide is selected from the groupconsisting of the electroactive oxides of nickel, manganese, cobalt, andvanadium, and the electroactive sulfides of iron. In one embodiment, acathode includes one or more of the following materials: manganesedioxide, iodine, silver chromate, silver oxide and vanadium pentoxide,copper oxide, copper oxyphosphate, lead sulfide, copper sulfide, ironsulfide, lead bismuthate, bismuth trioxide, cobalt dioxide, copperchloride, manganese dioxide, and carbon. In another embodiment, thecathode active layer comprises an electroactive conductive polymer.Examples of suitable electroactive conductive polymers include, but arenot limited to, electroactive and electronically conductive polymersselected from the group consisting of polypyrroles, polyanilines,polyphenylenes, polythiophenes, and polyacetylenes. Examples ofconductive polymers include polypyrroles, polyanilines, andpolyacetylenes.

In some embodiments, electroactive materials for use as cathode activematerials in electrochemical cells described herein includeelectroactive sulfur-containing materials. “Electroactivesulfur-containing materials,” as used herein, relates to cathode activematerials which comprise the element sulfur in any form, wherein theelectrochemical activity involves the oxidation or reduction of sulfuratoms or moieties. The nature of the electroactive sulfur-containingmaterials useful in the practice of this invention may vary widely, asknown in the art. For example, in one embodiment, the electroactivesulfur-containing material comprises elemental sulfur. In anotherembodiment, the electroactive sulfur-containing material comprises amixture of elemental sulfur and a sulfur-containing polymer. Thus,suitable electroactive sulfur-containing materials may include, but arenot limited to, elemental sulfur and organic materials comprising sulfuratoms and carbon atoms, which may or may not be polymeric. Suitableorganic materials include those further comprising heteroatoms,conductive polymer segments, composites, and conductive polymers.

In some embodiments, an electroactive sulfur-containing material of acathode active layer comprises greater than 50% by weight of sulfur. Inanother embodiment, the electroactive sulfur-containing materialcomprises greater than 75% by weight of sulfur. In yet anotherembodiment, the electroactive sulfur-containing material comprisesgreater than 90% by weight of sulfur.

The cathode active layers of the present invention may comprise fromabout 20 to 100% by weight of electroactive cathode materials (e.g., asmeasured after an appropriate amount of solvent has been removed fromthe cathode active layer and/or after the layer has been appropriatelycured). In one embodiment, the amount of electroactive sulfur-containingmaterial in the cathode active layer is in the range of 5-30% by weightof the cathode active layer. In another embodiment, the amount ofelectroactive sulfur-containing material in the cathode active layer isin the range of 20% to 90% by weight of the cathode active layer.

Additional materials suitable for use in the cathode, and suitablemethods for making the cathodes, are described, for example, in U.S.Pat. No. 5,919,587, filed May 21, 1997, entitled “Novel CompositeCathodes, Electrochemical Cells Comprising Novel Composite Cathodes, andProcesses for Fabricating Same,” and U.S. Patent Publication No.2010/0035128 to Scordilis-Kelley et al. filed on Aug. 4, 2009, entitled“Application of Force in Electrochemical Cells,” each of which isincorporated herein by reference in its entirety for all purposes.

A variety of electrolytes can be used in association with theelectrochemical cells described herein. In some embodiments, theelectrolyte may comprise a non-solid electrolyte, which may or may notbe incorporated with a porous separator. As used herein, the term“non-solid” is used to refer to materials that are unable to withstand astatic shear stress, and when a shear stress is applied, the non-solidexperiences a continuing and permanent distortion. Examples ofnon-solids include, for example, liquids, deformable gels, and the like.

The electrolytes used in electrochemical cells described herein canfunction as a medium for the storage and transport of ions, and in thespecial case of solid electrolytes and gel electrolytes, these materialsmay additionally function as a separator between the anode and thecathode. Any liquid, solid, or gel material capable of storing andtransporting ions may be used, so long as the material facilitates thetransport of ions (e.g., lithium ions) between the anode and thecathode. Exemplary materials suitable for use in the electrolyte aredescribed, for example, in U.S. Patent Publication No. 2010/0035128 toScordilis-Kelley et al. filed on Aug. 4, 2009, entitled “Application ofForce in Electrochemical Cells,” which is incorporated herein byreference in its entirety for all purposes.

U.S. Provisional Application No. 62/712,761, filed Jul. 31, 2018, andentitled “Multiplexed Charge Discharge Battery Management System” isincorporated herein by reference in its entirety for all purposes.

The following documents are incorporated herein by reference in theirentireties for all purposes: U.S. Pat. No. 7,247,408, filed May 23,2001, entitled “Lithium Anodes for Electrochemical Cells”; U.S. Pat. No.5,648,187, filed Mar. 19, 1996, entitled “Stabilized Anode forLithium-Polymer Batteries”; U.S. Pat. No. 5,961,672, filed Jul. 7, 1997,entitled “Stabilized Anode for Lithium-Polymer Batteries”; U.S. Pat. No.5,919,587, filed May 21, 1997, entitled “Novel Composite Cathodes,Electrochemical Cells Comprising Novel Composite Cathodes, and Processesfor Fabricating Same”; U.S. patent application Ser. No. 11/400,781,filed Apr. 6, 2006, published as U. S. Pub. No. 2007-0221265, andentitled “Rechargeable Lithium/Water, Lithium/Air Batteries”;International Patent Apl. Serial No.: PCT/US2008/009158, filed Jul. 29,2008, published as International Pub. No. WO/2009017726, and entitled“Swelling Inhibition in Lithium Batteries”; U.S. patent application Ser.No. 12/312,764, filed May 26, 2009, published as U.S. Pub. No.2010-0129699, and entitled “Separation of Electrolytes”; InternationalPatent Apl. Serial No.: PCT/US2008/012042, filed Oct. 23, 2008,published as International Pub. No. WO/2009054987, and entitled “Primerfor Battery Electrode”; U.S. patent application Ser. No. 12/069,335,filed Feb. 8, 2008, published as U.S. Pub. No. 2009-0200986, andentitled “Protective Circuit for Energy-Storage Device”; U.S. patentapplication Ser. No. 11/400,025, filed Apr. 6, 2006, published as U.S.Pub. No. 2007-0224502, and entitled “Electrode Protection in bothAqueous and Non-Aqueous Electrochemical Cells, including RechargeableLithium Batteries”; U.S. patent application Ser. No. 11/821,576, filedJun. 22, 2007, published as U.S. Pub. No. 2008/0318128, and entitled“Lithium Alloy/Sulfur Batteries”; patent application Ser. No.11/111,262, filed Apr. 20, 2005, published as U.S. Pub. No.2006-0238203, and entitled “Lithium Sulfur Rechargeable Battery FuelGauge Systems and Methods”; U.S. patent application Ser. No. 11/728,197,filed Mar. 23, 2007, published as U.S. Pub. No. 2008-0187663, andentitled “Co-Flash Evaporation of Polymerizable Monomers andNon-Polymerizable Carrier Solvent/Salt Mixtures/Solutions”;International Patent Apl. Serial No.: PCT/US2008/010894, filed Sep. 19,2008, published as International Pub. No. WO/2009042071, and entitled“Electrolyte Additives for Lithium Batteries and Related Methods”;International Patent Apl. Serial No.: PCT/US2009/000090, filed Jan. 8,2009, published as International Pub. No. WO/2009/089018, and entitled“Porous Electrodes and Associated Methods”; U.S. patent application Ser.No. 12/535,328, filed Aug. 4, 2009, published as U.S. Pub. No.2010/0035128, and entitled “Application of Force In ElectrochemicalCells”; U.S. patent application Ser. No. 12/727,862, filed Mar. 19,2010, entitled “Cathode for Lithium Battery”; U.S. patent applicationSer. No. 12/471,095, filed May 22, 2009, entitled “Hermetic SampleHolder and Method for Performing Microanalysis Under ControlledAtmosphere Environment”; U.S. patent application Ser. No. 12/862,513,filed on Aug. 24, 2010, entitled “Release System for Electrochemicalcells (which claims priority to Provisional Patent Apl. Ser. No.61/236,322, filed Aug. 24, 2009, entitled “Release System forElectrochemical Cells”); U.S. Provisional Patent Apl. Ser. No.61/376,554, filed on Aug. 24, 2010, entitled “ElectricallyNon-Conductive Materials for Electrochemical Cells;” U.S. Provisionalpatent application Ser. No. 12/862,528, filed on Aug. 24, 2010, entitled“Electrochemical Cell;” U.S. patent application Ser. No. 12/862,563,filed on Aug. 24, 2010, published as U.S. Pub. No. 2011/0070494,entitled “Electrochemical Cells Comprising Porous Structures ComprisingSulfur” [51583.70029US00]; U.S. patent application Ser. No. 12/862,551,filed on Aug. 24, 2010, published as U.S. Pub. No. 2011/0070491,entitled “Electrochemical Cells Comprising Porous Structures ComprisingSulfur” [51583.70030US00]; U.S. patent application Ser. No. 12/862,576,filed on Aug. 24, 2010, published as U.S. Pub. No. 2011/0059361,entitled “Electrochemical Cells Comprising Porous Structures ComprisingSulfur” [51583.70031US00]; U.S. patent application Ser. No. 12/862,581,filed on Aug. 24, 2010, published as U.S. Pub. No. 2011/0076560,entitled “Electrochemical Cells Comprising Porous Structures ComprisingSulfur” [51583.70024US01]; U.S. Patent Apl. Ser. No. 61/385,343, filedon Sep. 22, 2010, entitled “Low Electrolyte Electrochemical Cells”[51583.70033US00]; and U.S. patent application Ser. No. 13/033,419,filed Feb. 23, 2011, entitled “Porous Structures for Energy StorageDevices” [51583.70034US00]. All other patents and patent applicationsdisclosed herein are also incorporated by reference in their entiretyfor all purposes.

FIG. 4A depicts a representative high-level process 400A for dischargingsets of cells of a battery. The acts comprising representative process400A are described in detail in the paragraphs that follow.

In some embodiments, representative process 400A may include act 430,wherein sets of cells in a battery may be selectively discharged basedon at least one criterion using a multiplexing switch apparatus (such asmultiplexing switch apparatus 112 described above). Additionally, themultiplexing switch apparatus may be connected to two or more sets(e.g., 121, 122, 123, and/or 124) of cells (e.g., 121A-C) of at leastone battery (e.g., 120-150). Each set of cells may comprise one or morecells.

In some embodiments, process 400A may then end or repeat as necessary.

FIG. 4B depicts a representative high-level process 400B for dischargingsets of cells of a battery. The acts comprising representative process400B are described in detail in the paragraphs that follow.

In some embodiments, representative process 400B optionally may begin atact 410, wherein the multiplexing switch apparatus may be used toconnect the sets of cells to a load in a topology employed by the load.The batteries (e.g., 120-150) may include sets (e.g., 121, 122, 123,and/or 124) of the cells (e.g., 121A-C), and each set of cells maycomprise one or more cells. For example, the multiplexing switchapparatus may connect the cells to the load in series, parallel,serial/parallel, or any other suitable topology required to meet thevoltage and current requirements of the load or the desires of the givenapplication or user.

In some embodiments, representative process 400B may then optionallyproceed to act 420, wherein at least one criterion, and/or someparameter of a criterion, may be measured or otherwise monitored inrelation to the cells of the battery or batteries, which may already bedischarging or have discharged at least one cell or set of cells, todetermine whether the criterion has been met.

For example, a sensor (such as 116 in FIG. 1) may measure the delivereddischarge capacity at a connection between a load and a set of cellscurrently connected to the load, or it may measure the current of theset of cells. Alternatively or additionally, the sensor may measure anyof the following: a duration of the connection (which may be at least0.01 seconds in some embodiments), a capacity accumulated over severalconnections between the load and the set of cells, a voltage of the setof cells and/or of at least one other set of cells, a cutoff dischargevoltage of the set of cells, a power of the set of cells, an energy ofthe set of cells, a number of charge or discharge cycles of the set ofcells, an impedance of the set of cells, a rate of voltage fading of theset of cells during the connection, a temperature of the set of cells,and a pressure of the set of cells.

In some embodiments, the criterion may include a sequence in which todischarge the cells or sets of cells. Alternatively or additionally, thecriterion may be the value of a function that has any of the above asparameters. According to some embodiments, the criterion does notinclude a number of prior discharge cycles of the sets of cells.

In some embodiments, if the criterion has been met, representativeprocess 400B may then proceed to act 430, wherein the next set of cellsin the battery may be selectively discharged based on the criterionusing a multiplexing switch apparatus (such as multiplexing switchapparatus 112 described above). For example, if the current dischargingset of cells has met whatever criterion or criteria is required, thatset of cells may be disconnected and the next set of cells may beconnected (where the next set may be determined by a criterion orcriteria which may be the same or different from those discussed above)as described herein. Alternatively, if the criterion has not been met,it may continue to be monitored. According to some embodiments, theconnection between a single cell and the load may be at least 0.01seconds in duration. The inventors have recognized and appreciated thata shorter connection duration than 0.01 seconds may surprisingly producemore noise than at 0.01 seconds and may not allow the electrochemistryof the cell to accomplish anything non-negligible.

In some embodiments, representative process 400B may then optionallyproceed to act 431, wherein the multiplexing switch apparatus may beused to isolate a single set of cells for discharging while other setsof cells are not discharging. For example, when a controller (e.g., 114of FIG. 1) determines that cell 121B should be discharged, it may causethe multiplexing switch apparatus to isolate cell 121B for dischargingwhile cells 121A and 121C are not discharging.

In some embodiments, representative process 400B may then optionallyproceed to any of acts 432, 434, 436, and/or 438. For example, ifprocess 400B proceeds from act 431 to act 432, the multiplexing switchapparatus may be used to selectively discharge the sets of cells at afirst rate at least 2 times higher than a second rate of charging thesets of cells.

Alternatively or additionally, process 400B may proceed from act 431 toact 434, wherein the multiplexing switch apparatus may be used toselectively discharge the sets of cells at a first rate at least 4 timeshigher than a second rate of charging the sets of cells.

Alternatively or additionally, process 400B may proceed from act 431 toact 436, wherein discharge of the sets of cells may be temporallyoverlapping, such as by using the multiplexing switch apparatus asdiscussed above.

Alternatively or additionally, process 400B may proceed from act 431 toact 438, wherein power may continue to be provided from the sets ofcells during switching between different sets.

It should be appreciated that any of acts 431, 432, 434, 436, and/or 438may actually be integral to act 430, although they are represented asseparate acts in FIG. 4B.

In some embodiments, representative process 400B may then optionallyproceed to act 440, wherein the multiplexing switch apparatus may beused to charge the sets of cells in parallel, such as is describedabove.

According to some embodiments, any number of sets of cells, includingall the sets of cells in the battery, battery pack, or system, may bedischarged simultaneously. For example, with a battery having 4 cells,all 4 cells (or only 2 or 3) could be discharged at the same time,producing whatever discharge current is desirable for the load orapplication and possible for the cells. Additionally, in someembodiments, the number of cells or sets discharged or charged isselected based on the at least one criterion, such as discharge currentfor discharging. In certain embodiments, the sequence in which thenumber of cells or sets of cells is discharged or charged is selectedbased on the at least one criterion, such as discharge current fordischarging. In some embodiments, both the number of cells or setsdischarged or charged and the sequence of doing so is selected based onthe at least one criterion, such as discharge current for discharging.

In some embodiments, process 400B may then end or repeat as necessary.For example, process 400B may repeat through any suitable number ofcycles. According to some embodiments, for each cycle or some cycles,each cell may be discharged once before any cell is discharged twice.

FIG. 5 depicts a representative high-level process 500 for controlling abattery pack. The acts comprising representative process 500 aredescribed in detail in the paragraphs that follow.

In some embodiments, representative process 500 may include act 530,wherein switches may be controlled (e.g., by a controller such as 114described above) to discharge sets (e.g., 121, 122, 123, and/or 124) ofcells (e.g., 121A-C) in the battery pack (e.g., 210) sequentially usingan integrated switching control system. Additionally, the multiplexingswitch apparatus may be connected to two or more sets of cells of thebattery or batteries. Each set of cells may comprise one or more cells.

In some embodiments, process 500 may then end or repeat as necessary.

FIG. 6 depicts a representative high-level process 600 for controlling abattery pack. The acts comprising representative process 600 aredescribed in detail in the paragraphs that follow.

In some embodiments, representative process 600 may include act 630,wherein switches may be controlled (e.g., by a controller such as 114described above) to discharge sets (e.g., 121, 122, 123, and/or 124) ofcells (e.g., 121A-C) in the battery pack (e.g., 210) based on acriterion using an integrated switching control system. Additionally,the multiplexing switch apparatus may be connected to two or more setsof cells of the battery or batteries. Each set of cells may comprise oneor more cells. In some embodiments, the criterion may include any of thefollowing: a duration of a connection between a load and a set of cellscurrently connected to the load, a delivered discharge capacity at theconnection, and a value of a function having one or more parameters.

In some embodiments, process 600 may then end or repeat as necessary.

The inventors have recognized and appreciated that some embodimentsdescribed above may produce results showing various improvements overconventional techniques when implemented. For example, in oneimplementation, cells were made of NCMA622 cathode (BASF) with 50 μm Lifoil and 25 μm Celgard 2325 separator filled with F9 (BASF) electrolytecontaining 1% by weight of LiBOB, with an active electrode area of 99.41cm². The cells were assembled into 13 batteries containing 4 cells each.The batteries were subjected to 13 electrical charge-discharge cyclingtests performed using some embodiments at conditions summarized in Table1 and Table 2 below. The cells in the batteries were kept at pressure of12 kg/cm² and temperature of 18° C. during cycling tests.

TABLE 1 Battery test data for 4 cells simultaneously discharged witheven current distribution. Battery Battery 5^(th) Battery Battery CycleLife Cycle Cell Cell Discharge Charge to Discharge Discharge Charge TestCurrent Current 800 mAh Capacity Current Current # mA mA Cutoff mAh mAmA 1 800 800 29 1344 200 200 2 400 400 52 1380 100 100 3 300 300 53 141275 75

TABLE 2 Battery test data for 4 cells sequentially discharged at variousdischarge pulse durations. Battery Battery Cell Cell Level of BatteryBattery Cycle 5^(th) Cycle Discharge Discharge Cell No Cell CellDischarge Charge Life to Discharge Pulse Pulse Current Charge DischargeCurrent Current 800 mAh Capacity Current Duration Duration Current atSingle Test # mA mA Cutoff mAh mA s s mA Pulse 4 800 800 94 1064 8001197 0 200 Full 5 800 800 131 1208 800 10 30 200 Partial 6 800 800 1251252 800 1 3 200 Partial 7 800 800 46 1260 800 0.1 0.3 200 Partial 8 400400 263 1260 400 2835 0 100 Full 9 400 400 283 1284 400 10 30 100Partial 10 400 400 217 1352 400 1 3 100 Partial 11 400 400 59 1368 4000.1 0.3 100 Partial 12 300 300 334 1304 300 3912 0 75 Full 13 300 300298 1412 300 10 30 75 Partial

Table 1 (Tests #1-#3) represents comparative examples (as performed byconventional techniques) and summarizes test results when batteries werecharged and discharged at constant currents with cells connected inparallel and with charge and discharge currents distributed evenly among4 cells. Charge cutoff voltage was 4.35 V and discharge cutoff voltagewas 3.2 V. Charge-discharge cycling stopped when battery capacityreached 800 mAh.

Table 2 (Tests #4-#13) summarizes test results when batteries werecharged to 4.35 V at constant currents with cells connected in paralleland with charge discharge currents distributed evenly among 4 cells.Discharge of these batteries was performed in a way that the battery asa whole experienced constant discharge current. However, individualcells were connected to and disconnected from the load sequentially,providing discharge current pulse only for one of four cells at a time.At the end of this pulse, the next cell was connected and the previousone was disconnected. Cells experienced discharge pulses in sequences(e.g., Cell #1, 2, 3, 4, 1, 2, 3, 4, etc.) during a certain pulse timeor until discharge voltage reached 3.2 V. Tests #4, #8, and #12 providedfull cell discharge at single pulse. Other tests provided partial celldischarge at single pulse with durations of 0.1, 1, and 10 s.Charge-discharge cycling stopped when battery capacity reached 800 mAh.

FIG. 7A, corresponding to Test #13, shows the battery voltage profile atthe beginning of the 10 second pulse discharge for the first 240seconds, and FIG. 7B shows the full discharge profile to a voltage of3.2 V. In FIG. 7A, the cell numbers affected by the 10 second 300 mApulses at repeated sequences are shown for the first 80 seconds.

Referring back to Table 1 and Table 2, the inventors have recognized andappreciated that applying whole battery discharge current to the portionof the battery cells in sequence (Table 2) has led to surprising anddramatic cycle life improvement compared with homogeneous currentdistribution among all battery cells (Table 1), as has been done inconventional techniques. This cycle life improvement may be up tosix-fold, and the inventors recognized it may be a function of dischargepulse duration as well as charge-discharge rate. FIG. 7C, whichillustrates battery cycle life as a function of pulse duration at twocharge-discharge rates (corresponding to Tests #4-#11), shows that cyclelife may be especially improved with pulse time longer than 0.1 secondsand pulse duration around 10 seconds. The inventors have recognized andappreciated that improvements to battery cycle life described herein areeven available using some embodiments at partial discharge, as FIG. 7Cshows and as would not have been expected based on experience withconventional techniques. Additionally, the full capacity of all cells,even when far from uniform, can be utilized with some embodiments.

It should be appreciated that, in some embodiments, the methodsdescribed above with reference to FIGS. 4A-6 may vary, in any ofnumerous ways. For example, in some embodiments, the steps of themethods described above may be performed in a different sequence thanthat which is described, a method may involve additional steps notdescribed above, and/or a method may not involve all of the stepsdescribed above.

It should further be appreciated from the foregoing description thatsome aspects may be implemented using a computing device. FIG. 8 depictsa general purpose computing device in system 800, in the form of acomputer 810, which may be used to implement certain aspects, such asany of the controllers described above (e.g., 114).

In computer 810, components include, but are not limited to, aprocessing unit 820, a system memory 830, and a system bus 821 thatcouples various system components including the system memory to theprocessing unit 820. The system bus 821 may be any of several types ofbus structures including a memory bus or memory controller, a peripheralbus, and a local bus using any of a variety of bus architectures. By wayof example, and not limitation, such architectures include IndustryStandard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus,Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA)local bus, and Peripheral Component Interconnect (PCI) bus also known asMezzanine bus.

Computer 810 typically includes a variety of computer readable media.Computer readable media can be any available media that can be accessedby computer 810 and includes both volatile and nonvolatile media,removable and non-removable media. By way of example, and notlimitation, computer readable media may comprise computer storage mediaand communication media. Computer storage media includes both volatileand nonvolatile, removable and non-removable media implemented in anymethod or technology for storage of information such as computerreadable instructions, data structures, program modules or other data.Computer storage media include, but are not limited to, RAM, ROM,EEPROM, flash memory or other memory technology, CD-ROM, digitalversatile disks (DVD) or other optical disk storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other one or more media that may be used to store the desiredinformation and may be accessed by computer 810. Communication mediatypically embody computer readable instructions, data structures,program modules or other data in a modulated data signal such as acarrier wave or other transport mechanism and includes any informationdelivery media. The term “modulated data signal” means a signal that hasone or more of its characteristics set or changed in such a manner as toencode information in the signal. By way of example, and not limitation,communication media include wired media such as a wired network ordirect-wired connection, and wireless media such as acoustic, RF,infrared and other wireless media. Combinations of the any of the aboveshould also be included within the scope of computer readable media.

The system memory 830 includes computer storage media in the form ofvolatile and/or nonvolatile memory such as read only memory (ROM) 831and random access memory (RAM) 832. A basic input/output system 833(BIOS), containing the basic routines that help to transfer informationbetween elements within computer 810, such as during start-up, istypically stored in ROM 831. RAM 832 typically contains data and/orprogram modules that are immediately accessible to and/or presentlybeing operated on by processing unit 820. By way of example, and notlimitation, FIG. 8 illustrates operating system 834, applicationprograms 835, other program modules 839 and program data 837.

The computer 810 may also include other removable/non-removable,volatile/nonvolatile computer storage media. By way of example only,FIG. 8 illustrates a hard disk drive 841 that reads from or writes tonon-removable, nonvolatile magnetic media, a magnetic disk drive 851that reads from or writes to a removable, nonvolatile magnetic disk 852,and an optical disk drive 855 that reads from or writes to a removable,nonvolatile optical disk 859 such as a CD ROM or other optical media.Other removable/non-removable, volatile/nonvolatile computer storagemedia that can be used in the exemplary computing system include, butare not limited to, magnetic tape cassettes, flash memory cards, digitalversatile disks, digital video tape, solid state RAM, solid state ROM,and the like. The hard disk drive 841 is typically connected to thesystem bus 821 through an non-removable memory interface such asinterface 840, and magnetic disk drive 851 and optical disk drive 855are typically connected to the system bus 821 by a removable memoryinterface, such as interface 850.

The drives and their associated computer storage media discussed aboveand illustrated in FIG. 8, provide storage of computer readableinstructions, data structures, program modules and other data for thecomputer 810. In FIG. 8, for example, hard disk drive 841 is illustratedas storing operating system 844, application programs 845, other programmodules 849, and program data 847. Note that these components can eitherbe the same as or different from operating system 834, applicationprograms 835, other program modules 539, and program data 837. Operatingsystem 844, application programs 845, other program modules 849, andprogram data 847 are given different numbers here to illustrate that, ata minimum, they are different copies. A user may enter commands andinformation into the computer 810 through input devices such as akeyboard 892 and pointing device 891, commonly referred to as a mouse,trackball or touch pad. Other input devices (not shown) may include amicrophone, joystick, game pad, satellite dish, scanner, or the like.These and other input devices are often connected to the processing unit820 through a user input interface 590 that is coupled to the systembus, but may be connected by other interface and bus structures, such asa parallel port, game port or a universal serial bus (USB). A monitor891 or other type of display device is also connected to the system bus821 via an interface, such as a video interface 890. In addition to themonitor, computers may also include other peripheral output devices suchas speakers 897 and printer 899, which may be connected through a outputperipheral interface 895.

The computer 810 may operate in a networked environment using logicalconnections to one or more remote computers, such as a remote computer880. The remote computer 880 may be a personal computer, a server, arouter, a network PC, a peer device or other common network node, andtypically includes many or all of the elements described above relativeto the computer 810, although only a memory storage device 881 has beenillustrated in FIG. 8. The logical connections depicted in FIG. 8include a local area network (LAN) 871 and a wide area network (WAN)873, but may also include other networks. Such networking environmentsare commonplace in offices, enterprise-wide computer networks, intranetsand the Internet.

When used in a LAN networking environment, the computer 810 is connectedto the LAN 871 through a network interface or adapter 870. When used ina WAN networking environment, the computer 810 typically includes amodem 872 or other means for establishing communications over the WAN873, such as the Internet. The modem 872, which may be internal orexternal, may be connected to the system bus 821 via the user inputinterface 890, or other appropriate mechanism. In a networkedenvironment, program modules depicted relative to the computer 810, orportions thereof, may be stored in the remote memory storage device. Byway of example, and not limitation, FIG. 8 illustrates remoteapplication programs 885 as residing on memory device 881. It will beappreciated that the network connections shown are exemplary and othermeans of establishing a communications link between the computers may beused.

Embodiments may be embodied as a computer readable storage medium (ormultiple computer readable media) (e.g., a computer memory, one or morefloppy discs, compact discs (CD), optical discs, digital video disks(DVD), magnetic tapes, flash memories, circuit configurations in FieldProgrammable Gate Arrays or other semiconductor devices, or othertangible computer storage medium) encoded with one or more programsthat, when executed on one or more computers or other processors,perform methods that implement the various embodiments discussed above.As is apparent from the foregoing examples, a computer readable storagemedium may retain information for a sufficient time to provide computerexecutable instructions in a non-transitory form. Such a computerreadable storage medium or media can be transportable, such that theprogram or programs stored thereon can be loaded onto one or moredifferent computers or other processors to implement various aspects ofthe present invention as discussed above. As used herein, the term“computer-readable storage medium” encompasses only a tangible machine,mechanism or device from which a computer may read information.Alternatively or additionally, some embodiments may be embodied as acomputer readable medium other than a computer-readable storage medium.Examples of computer readable media that are not computer readablestorage media include transitory media, like propagating signals.

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention may include each individual feature, system, article,material, and/or method described herein. In addition, any combinationof two or more such features, systems, articles, materials, and/ormethods, if such features, systems, articles, materials, and/or methodsare not mutually inconsistent, is included within the scope of thepresent invention.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Other elements may optionallybe present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elementsspecifically identified unless clearly indicated to the contrary. Thus,as a non-limiting example, a reference to “A and/or B,” when used inconjunction with open-ended language such as “comprising” can refer, inone embodiment, to A without B (optionally including elements other thanB); in another embodiment, to B without A (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

Some embodiments may be embodied as a method, of which various exampleshave been described. The acts performed as part of the methods may beordered in any suitable way. Accordingly, embodiments may be constructedin which acts are performed in an order different than illustrated,which may include different (e.g., more or less) acts than those thatare described, and/or that may involve performing some actssimultaneously, even though the acts are shown as being performedsequentially in the embodiments specifically described above.

Use of ordinal terms such as “first,” “second,” “third,” etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” and the like are to be understoodto be open-ended, i.e., to mean including but not limited to. Only thetransitional phrases “consisting of” and “consisting essentially of”shall be closed or semi-closed transitional phrases, respectively, asset forth in the United States Patent Office Manual of Patent ExaminingProcedures, Section 2111.03.

What is claimed is:
 1. A battery management system comprising: at leastone battery comprising two or more sets of cells, each set of cellscomprising one or more cells; a multiplexing switch apparatus connectedto each set of cells; and at least one controller configured to use themultiplexing switch apparatus to selectively discharge the sets of cellsat a discharging rate at least 2 times higher than a charging rate ofthe sets of cells; wherein for a given cycle, each cell is dischargedonce before any cell is discharged twice.
 2. The battery managementsystem of claim 1, wherein the discharging rate is 4 times higher thanthe charging rate.
 3. The battery management system of claim 1, whereinthe at least one controller is configured to temporally overlap thedischarge of the sets of cells.
 4. The battery management system ofclaim 1, wherein the at least one controller is configured to continueto provide power from the sets of cells during switching betweendifferent sets.
 5. The battery management system of claim 1, wherein atleast one controller is configured to use the multiplexing switchapparatus to apply the charging rate of the sets of cells prior to thedischarging rate.
 6. A battery pack comprising: at least one batterycomprising two or more sets of cells, each set of cells comprising oneor more cells; and an integrated switching control system comprising atleast one switch connected to each set of cells, wherein: the integratedswitching control system is configured to control the at least oneswitch to discharge the sets of cells at a discharging rate at least 2times higher than a charging rate of the sets of cells, and for a givencycle, each cell is discharged once before any cell is discharged twice.7. The battery pack of claim 6, wherein the discharging rate is 4 timeshigher than the charging rate.
 8. The battery pack of claim 6, whereinthe integrated switching control system is configured to control the atleast one switch to temporally overlap the discharge of the sets ofcells.
 9. The battery pack of claim 6, wherein the integrated switchingcontrol system is configured to control the at least one switch tocontinue to provide power from the sets of cells during switchingbetween different sets.
 10. A battery management method comprising:using a multiplexing switch apparatus, which is connected to two or moresets of cells of at least one battery, to selectively discharge each setof cells at a discharging rate at least 2 times higher than a chargingrate of the sets of cells, wherein: each set of cells comprises one ormore cells, and for a given cycle, each cell is discharged once beforeany cell is discharged twice.
 11. The battery management method of claim10, wherein the discharging rate is 4 times higher than the chargingrate.
 12. The battery management method of claim 10, further comprisingtemporally overlapping discharge of sets of cells.
 13. The batterymannagement method of claim 10, further comprising continuing to providepower from the sets of cells during switching between different sets.14. An electrochemical cell controlled by the battery management methodof claim
 10. 15. A rechargeable battery comprising the electrochemicalcell of claim
 14. 16. A vehicle comprising the rechargeable battery ofclaim
 15. 17. A vehicle comprising the electrochemical cell of claim 14.